1. Field of the Invention
The present invention relates to an electromagnetic shielding material and more particularly to an electromagnetic shielding material comprising a pyrrole polymer complex consisting of (i) repeated pyrrole monomer units which constitute the main chain of the polymer complex and (ii) aromatic anions bonded to the main chain.
2. Discussion of the Background
In most recent electronic apparatus and devices, for instance, computers, IC and LSI are employed. From such apparatus and devices, electromagnetic waves are generated in the form of high frequency pulses and leak, having significant adverse effects on the peripheral equipment.
Conventionally, in order to prevent the leakage of such electromagnetic waves from such electronic apparatus and devices and to avoid the electromagnetic interference with the peripheral equipment, the following two methods are conventionally proposed.
The first method is a surface treatment method of forming an electroconductive thin layer on the surface of a plastic molded housing. The second method is a molding method of molding a plastic housing in which an electroconductive filler is dispersed. See, for example, the February 1986 issue of "Appliance."
The first method, however, has the shortcomings that (i) when metal plating is performed, the resins that can be employed with metal plating are limited to particular kinds of resins, (ii) when a metal-foil adhesive tape is applied to a housing, the applied housing becomes heavy, and (iii) when an electroconductive paint is employed, the coating thickness must be as great as 50 .mu.m or more to form a uniform coated layer and a sufficient shielding effect for use in practice cannot always be obtained by such electroconductive painting.
In the second method, it is necessary to add about 30 wt.% to 40 wt.% of an electroconductive filler to the plastics for molding housings. The result is that the mechanically strong electromagnetic-shielded housings cannot be obtained.
Apart from the above, it is conventionally known that polymers having conjugated double bonds in the main chains, such as polyacetylene and polythiophene, can be made almost as electroconductive as metals by addition as dopant of an extremely small amount of impurities, such as BF.sub.4.sup.-, BF.sub.3, Cl, Br and I. These polymers, however, are not stable when exposed to the air, since such dopants are easily released and therefore cannot maintain high electroconductivity for a long period of time. Furthermore, the mechanical strength of such polymers is insufficient for practical use. Therefore, these polymers cannot be employed in practice as electromagnetic shielding material.